Book Image

Professional Scala

By : Mads Hartmann, Ruslan Shevchenko
Book Image

Professional Scala

By: Mads Hartmann, Ruslan Shevchenko

Overview of this book

This book teaches you how to build and contribute to Scala programs, recognizing common patterns and techniques used with the language. You’ll learn how to write concise, functional code with Scala. After an introduction to core concepts, syntax, and writing example applications with scalac, you’ll learn about the Scala Collections API and how the language handles type safety via static types out-of-the-box. You’ll then learn about advanced functional programming patterns, and how you can write your own Domain Specific Languages (DSLs). By the end of the book, you’ll be equipped with the skills you need to successfully build smart, efficient applications in Scala that can be compiled to the JVM.
Table of Contents (12 chapters)


In this section, we will introduce the fundamentals of functional programming, such as function values and high-order functions.

Function Values

What is a function? We are familiar with methods, which must be defined in a scope (class or objects):

  def f1(x:Int, y:Int): Int =  x + y

In Scala, we can also define a function value:

   val f2: (Int,Int) => Int = (x,y) => (x+y).

Here, we define the function value, with a type of (Int,Int) => Int. Of course, as with all type declarations, the type can be omitted if it can be deduced from the context. So, an alternative syntax for this can be:

   val f2 = (x:Int,y:Int) => (x+y).

Both f1(1,2) and f2(1,2) will force evaluation. The difference between f1 and f2 is that the second is a value, which can be stored in a variable or passed to another function.

Functions which accept other functions as parameters are named high-order functions, for example:

def twice(f: Int => Int): Int => Int = x => f(f(x))

This function...